Rotatable X-ray target having off-focal track coating

Abstract

An X-ray tube including a tubular envelope having therein an anode target provided with a surface portion made of X-ray emissive material and with another surface portion made of heat emissive material comprising at least one of the members from the group consisting of hafnium boride, hafnium oxide, hafnium nitride, hafnium silicide, and hafnium aluminide; and an electron emitting cathode disposed to direct a beam of electrons onto the anode surface portion made of X-ray emissive material.

What is claimed is: 
     
       1. An X-ray target of the rotatable type adapted for mounting on a rotor and including: a body having a first surface portion made of X-ray emissive material and a second surface portion made of a heat emissive material comprised of at least ninety-five percent by weight hafnium compound, said compound being at least one of the members from the group consisting of hafnium boride, hafnium oxide, hafnium nitride, hafnium silicide, and hafnium aluminide.   
     
     
       2. An X-ray target as set forth in claim 1 wherein the body is a rotatable disc. 
     
     
       3. An X-ray target as set forth in claim 2 wherein the first surface portion is annular and disposed adjacent the outer periphery of the disc. 
     
     
       4. An X-ray target as set forth in claim 1 wherein the second surface portion comprises a coating mechanically and thermally coupled to body. 
     
     
       5. An X-ray target as set forth in claim 1 wherein the first surface portion comprises a coating mechanically and thermally coupled to the body. 
     
     
       6. An X-ray tube of the rotatable anode type including: an evacuable envelope;   an anode rotor rotatably supported within said envelope;   an X-ray target mounted on said rotor in the envelope and comprising a body having a first surface portion made of X-ray emissive material and a second surface portion made of heat emissive material comprised of at least ninety-five percent by weight hafnium compound, said compound being at least one of the members of the group consisting of hafnium boride, hafnium oxide, hafnium nitride, hafnium silicide, and hafnium aluminide; and   means disposed in the envelope for beaming electrons into the X-ray emissive material and generating X-rays.   
     
     
       7. An X-ray tube as set forth in claim 6 wherein said body of the target comprises a rotatable disc. 
     
     
       8. An X-ray tube as set forth in claim 7 wherein said first surface portion is annularly disposed adjacent the outer periphery of the disc. 
     
     
       9. An X-ray tube as set forth in claim 8 wherein the X-ray emissive material comprises a coating mechanically and thermally coupled to the disc. 
     
     
       10. An X-ray tube as set forth in claim 6 wherein the heat emissive material comprises a coating mechanically and thermally coupled to the disc.